Root/drivers/staging/echo/fir.h

1/*
2 * SpanDSP - a series of DSP components for telephony
3 *
4 * fir.h - General telephony FIR routines
5 *
6 * Written by Steve Underwood <steveu@coppice.org>
7 *
8 * Copyright (C) 2002 Steve Underwood
9 *
10 * All rights reserved.
11 *
12 * This program is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU General Public License version 2, as
14 * published by the Free Software Foundation.
15 *
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
20 *
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software
23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24 */
25
26#if !defined(_FIR_H_)
27#define _FIR_H_
28
29/*
30   Blackfin NOTES & IDEAS:
31
32   A simple dot product function is used to implement the filter. This performs
33   just one MAC/cycle which is inefficient but was easy to implement as a first
34   pass. The current Blackfin code also uses an unrolled form of the filter
35   history to avoid 0 length hardware loop issues. This is wasteful of
36   memory.
37
38   Ideas for improvement:
39
40   1/ Rewrite filter for dual MAC inner loop. The issue here is handling
41   history sample offsets that are 16 bit aligned - the dual MAC needs
42   32 bit aligmnent. There are some good examples in libbfdsp.
43
44   2/ Use the hardware circular buffer facility tohalve memory usage.
45
46   3/ Consider using internal memory.
47
48   Using less memory might also improve speed as cache misses will be
49   reduced. A drop in MIPs and memory approaching 50% should be
50   possible.
51
52   The foreground and background filters currenlty use a total of
53   about 10 MIPs/ch as measured with speedtest.c on a 256 TAP echo
54   can.
55*/
56
57/*
58 * 16 bit integer FIR descriptor. This defines the working state for a single
59 * instance of an FIR filter using 16 bit integer coefficients.
60 */
61struct fir16_state_t {
62    int taps;
63    int curr_pos;
64    const int16_t *coeffs;
65    int16_t *history;
66};
67
68/*
69 * 32 bit integer FIR descriptor. This defines the working state for a single
70 * instance of an FIR filter using 32 bit integer coefficients, and filtering
71 * 16 bit integer data.
72 */
73struct fir32_state_t {
74    int taps;
75    int curr_pos;
76    const int32_t *coeffs;
77    int16_t *history;
78};
79
80/*
81 * Floating point FIR descriptor. This defines the working state for a single
82 * instance of an FIR filter using floating point coefficients and data.
83 */
84struct fir_float_state_t {
85    int taps;
86    int curr_pos;
87    const float *coeffs;
88    float *history;
89};
90
91static inline const int16_t *fir16_create(struct fir16_state_t *fir,
92                          const int16_t *coeffs, int taps)
93{
94    fir->taps = taps;
95    fir->curr_pos = taps - 1;
96    fir->coeffs = coeffs;
97#if defined(__bfin__)
98    fir->history = kcalloc(2 * taps, sizeof(int16_t), GFP_KERNEL);
99#else
100    fir->history = kcalloc(taps, sizeof(int16_t), GFP_KERNEL);
101#endif
102    return fir->history;
103}
104
105static inline void fir16_flush(struct fir16_state_t *fir)
106{
107#if defined(__bfin__)
108    memset(fir->history, 0, 2 * fir->taps * sizeof(int16_t));
109#else
110    memset(fir->history, 0, fir->taps * sizeof(int16_t));
111#endif
112}
113
114static inline void fir16_free(struct fir16_state_t *fir)
115{
116    kfree(fir->history);
117}
118
119#ifdef __bfin__
120static inline int32_t dot_asm(short *x, short *y, int len)
121{
122    int dot;
123
124    len--;
125
126    __asm__("I0 = %1;\n\t"
127        "I1 = %2;\n\t"
128        "A0 = 0;\n\t"
129        "R0.L = W[I0++] || R1.L = W[I1++];\n\t"
130        "LOOP dot%= LC0 = %3;\n\t"
131        "LOOP_BEGIN dot%=;\n\t"
132        "A0 += R0.L * R1.L (IS) || R0.L = W[I0++] || R1.L = W[I1++];\n\t"
133        "LOOP_END dot%=;\n\t"
134        "A0 += R0.L*R1.L (IS);\n\t"
135        "R0 = A0;\n\t"
136        "%0 = R0;\n\t"
137        : "=&d"(dot)
138        : "a"(x), "a"(y), "a"(len)
139        : "I0", "I1", "A1", "A0", "R0", "R1"
140    );
141
142    return dot;
143}
144#endif
145
146static inline int16_t fir16(struct fir16_state_t *fir, int16_t sample)
147{
148    int32_t y;
149#if defined(__bfin__)
150    fir->history[fir->curr_pos] = sample;
151    fir->history[fir->curr_pos + fir->taps] = sample;
152    y = dot_asm((int16_t *) fir->coeffs, &fir->history[fir->curr_pos],
153            fir->taps);
154#else
155    int i;
156    int offset1;
157    int offset2;
158
159    fir->history[fir->curr_pos] = sample;
160
161    offset2 = fir->curr_pos;
162    offset1 = fir->taps - offset2;
163    y = 0;
164    for (i = fir->taps - 1; i >= offset1; i--)
165        y += fir->coeffs[i] * fir->history[i - offset1];
166    for (; i >= 0; i--)
167        y += fir->coeffs[i] * fir->history[i + offset2];
168#endif
169    if (fir->curr_pos <= 0)
170        fir->curr_pos = fir->taps;
171    fir->curr_pos--;
172    return (int16_t) (y >> 15);
173}
174
175static inline const int16_t *fir32_create(struct fir32_state_t *fir,
176                          const int32_t *coeffs, int taps)
177{
178    fir->taps = taps;
179    fir->curr_pos = taps - 1;
180    fir->coeffs = coeffs;
181    fir->history = kcalloc(taps, sizeof(int16_t), GFP_KERNEL);
182    return fir->history;
183}
184
185static inline void fir32_flush(struct fir32_state_t *fir)
186{
187    memset(fir->history, 0, fir->taps * sizeof(int16_t));
188}
189
190static inline void fir32_free(struct fir32_state_t *fir)
191{
192    kfree(fir->history);
193}
194
195static inline int16_t fir32(struct fir32_state_t *fir, int16_t sample)
196{
197    int i;
198    int32_t y;
199    int offset1;
200    int offset2;
201
202    fir->history[fir->curr_pos] = sample;
203    offset2 = fir->curr_pos;
204    offset1 = fir->taps - offset2;
205    y = 0;
206    for (i = fir->taps - 1; i >= offset1; i--)
207        y += fir->coeffs[i] * fir->history[i - offset1];
208    for (; i >= 0; i--)
209        y += fir->coeffs[i] * fir->history[i + offset2];
210    if (fir->curr_pos <= 0)
211        fir->curr_pos = fir->taps;
212    fir->curr_pos--;
213    return (int16_t) (y >> 15);
214}
215
216#endif
217

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